Vehicle air conditioner

ABSTRACT

A vehicle air conditioner which is capable of inhibiting liquid return to a compressor and generation of noise due to bumping in an accumulator. There are executed a heating mode to close a solenoid valve  17 , open a solenoid valve  21 , let a refrigerant radiate heat in a radiator  4 , decompress the refrigerant through an outdoor expansion valve  6 , let the refrigerant absorb heat in an outdoor heat exchanger  7 , and send the refrigerant to an accumulator  12 , and a dehumidifying and heating mode to open the solenoid valve  17 , close the solenoid valve  21 , decompress the refrigerant through an indoor expansion valve  8 , let the refrigerant absorb heat in a heat absorber, and generate heat in an auxiliary heater  23 . A valve position of the outdoor expansion valve  6  is reduced for a predetermined period of time before shifting from the heating mode to the dehumidifying and heating mode.

RELATED APPLICATIONS

This is a U.S. National Phase Application under 35 USC 371 ofInternational Application PCT/JP2017/014891 filed on Apr. 5, 2017.

This application claims the priority of Japanese application no.2016-081231 filed Apr. 14, 2016, the entire content of which is herebyincorporated by reference.

TECHNICAL FIELD

The present invention relates to an air conditioner of a heat pumpsystem which conditions air of a vehicle interior, and moreparticularly, it relates to an air conditioner which is applicable to ahybrid car and an electric vehicle.

BACKGROUND ART

To cope with enhancement of environmental problems in recent years,hybrid cars and electric vehicles have spread. Furthermore, as an airconditioner which is applicable to such a vehicle, there has beendeveloped a device including a compressor to compress and discharge arefrigerant, a radiator disposed on the side of a vehicle interior tolet the refrigerant radiate heat, a heat absorber disposed on the sideof the vehicle interior to let the refrigerant absorb heat, and anoutdoor heat exchanger disposed outside the vehicle interior to let therefrigerant radiate heat or absorb heat, and there are changed andexecuted a heating mode to let the refrigerant discharged from thecompressor radiate heat in the radiator and decompress the refrigerantfrom which the heat has been radiated in this radiator through anoutdoor expansion valve and then let the refrigerant absorb heat in theoutdoor heat exchanger, a dehumidifying and heating mode or adehumidifying and cooling mode to let the refrigerant discharged fromthe compressor radiate heat in the radiator and the outdoor heatexchanger and decompress the refrigerant from which the heat has beenradiated through an indoor expansion valve and then let the refrigerantabsorb heat in the heat absorber, and a cooling mode to let therefrigerant discharged from the compressor radiate heat in the outdoorheat exchanger and decompress the refrigerant from which the heat hasbeen radiated through the indoor expansion valve and then let therefrigerant absorb heat in the heat absorber.

In this case, an accumulator is disposed on a refrigerant suction sideof the compressor. In the heating mode, a solenoid valve for cooling isclosed and a solenoid valve for heating is opened to send, to theaccumulator, the refrigerant flowing out from the outdoor heatexchanger. For example, in the dehumidifying and heating mode, thesolenoid valve for the heating is closed and the solenoid valve for thecooling is opened to send, to the indoor expansion valve, therefrigerant flowing out from the outdoor heat exchanger and todecompress the refrigerant, the refrigerant is evaporated in the heatabsorber, and the refrigerant flowing through this heat absorber is sentto the accumulator. In this constitution, the refrigerant is once storedin this accumulator, thereby performing gas-liquid separation therein,and thus separated gas refrigerant is sucked into the compressor, sothat liquid return to the compressor is prevented or inhibited (e.g.,see Patent Document 1).

CITATION LIST Patent Documents

Patent Document 1: Japanese Patent Application Publication No.2014-94671

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

Here, a refrigerant and oil flowing out from a compressor through arefrigerant circuit flow into an accumulator when a compressor isstopped, their liquid part is accumulated in the accumulator, and theoil having a smaller specific weight forms a layer on the liquidrefrigerant, thereby bringing about a stable state like a state of beingclosed with a lid. Particularly, in a heating mode to be executed in anenvironment where an outdoor air temperature is low, there increaseamounts of the liquid refrigerant and oil which flow out from an outdoorheat exchanger through a solenoid valve for heating into the accumulatorand are accumulated therein. Therefore, an oil surface (a liquid surfacein the accumulator) rises up to the vicinity of an outlet of theaccumulator.

In such a state, when a heating mode to decompress the refrigerantthrough an outdoor expansion valve changes to another operation mode todecompress the refrigerant through an indoor expansion valve (the abovedehumidifying and heating mode or dehumidifying and cooling mode, or acooling mode), the refrigerant flowing out from the outdoor heatexchanger flows on the side of the indoor expansion valve. On the otherhand, the compressor sucks the refrigerant in the accumulator, and hencea pressure in the accumulator rapidly drops. When the pressure in theaccumulator rapidly drops in this manner, a phenomenon of so-calledbumping occurs where the refrigerant below the oil boils and vaporizeswithout stopping, and intensely breaks through the upper oil layer.

Then, when this bumping intensifies, a lot of liquid refrigerant in theaccumulator is pushed out from the outlet, excessive liquid return tothe compressor accordingly occurs, and liquid compression impairsreliability of the compressor. Additionally, the bumping phenomenon inthe accumulator generates a comparatively large noise, and hence therehas also been the problem that comfort of passengers is impaired by thegeneration of the noise.

The present invention has been developed to solve such conventionaltechnical problems, and an object thereof is to provide a vehicle airconditioner which is capable of preventing or inhibiting liquid returnto a compressor and generation of noise in an accumulator, which occurwhen an operation mode to decompress a refrigerant through an outdoorexpansion valve is changed to another operation mode to decompress therefrigerant through an indoor expansion valve.

Means for Solving the Problems

A vehicle air conditioner of the invention includes a compressor tocompress a refrigerant, an air flow passage through which air to besupplied to a vehicle interior flows, a radiator to let the refrigerantradiate heat, thereby heating the air to be supplied from the air flowpassage to the vehicle interior, a heat absorber to let the refrigerantabsorb heat, thereby cooling the air to be supplied from the air flowpassage to the vehicle interior, an outdoor heat exchanger disposedoutside the vehicle interior, an outdoor expansion valve to decompressthe refrigerant flowing out from the radiator and flowing into theoutdoor heat exchanger, an indoor expansion valve to decompress therefrigerant flowing into the heat absorber, an accumulator connected toa refrigerant suction side of the compressor, a first opening/closingvalve to send the refrigerant flowing out from the outdoor heatexchanger, through the indoor expansion valve to the heat absorber, asecond opening/closing valve to send the refrigerant flowing out fromthe outdoor heat exchanger to the accumulator without passing the heatabsorber, and a control device, so that this control device switchesbetween and executes a first operation mode to close the firstopening/closing valve, open the second opening/closing valve, therebylet the refrigerant discharged from the compressor radiate heat in theradiator, decompress the refrigerant from which the heat has beenradiated, through the outdoor expansion valve, let the refrigerantabsorb heat in the outdoor heat exchanger, send, to the accumulator, therefrigerant flowing out from this outdoor heat exchanger, and suck therefrigerant from this accumulator into the compressor, and a secondoperation mode to open the first opening/closing valve, close the secondopening/closing valve, thereby decompress the refrigerant flowing outfrom the outdoor heat exchanger through the indoor expansion valve, letthe refrigerant absorb heat in the heat absorber, send, to theaccumulator, the refrigerant flowing out from this heat absorber, andsuck the refrigerant from this accumulator into the compressor, and thevehicle air conditioner is characterized in that when the control deviceshifts from the first operation mode to the second operation mode, avalve position of the outdoor expansion valve is reduced for apredetermined period of time before the shifting.

The vehicle air conditioner of the invention of claim 2 is characterizedin that in the above invention, the control device maintains a highnumber of revolution of the compressor for a predetermined period oftime before shifting to the second operation mode.

The vehicle air conditioner of the invention of claim 3 is characterizedin that the above respective inventions include a bypass pipe bypassingthe radiator and the outdoor expansion valve, to send, directly into theoutdoor heat exchanger, the refrigerant discharged from the compressor,a third opening/closing valve to send the refrigerant discharged fromthe compressor to the radiator, a fourth opening/closing valve to sendthe refrigerant discharged from the compressor to the bypass pipe, andan auxiliary heating device to heat the air to be supplied from the airflow passage to the vehicle interior, the first operation mode is aheating mode, and in this heating mode, the control device opens thethird opening/closing valve and closes the fourth opening/closing valve,and the second operation mode includes any one, any combination or allof a dehumidifying and heating mode to close the third opening/closingvalve and the outdoor expansion valve, open the fourth opening/closingvalve, thereby send the refrigerant discharged from the compressor fromthe bypass pipe to the outdoor heat exchanger, let the refrigerantradiate heat, decompress the refrigerant from which the heat has beenradiated, through the indoor expansion valve, let the refrigerant absorbheat in the heat absorber, and generate heat in the auxiliary heatingdevice, a dehumidifying and cooling mode to open the thirdopening/closing valve, close the fourth opening/closing valve, therebysend the refrigerant discharged from the compressor from the radiator tothe outdoor heat exchanger, let the refrigerant radiate heat in theradiator and the outdoor heat exchanger, decompress the refrigerant fromwhich the heat has been radiated, through the indoor expansion valve,and then let the refrigerant absorb heat in the heat absorber, a coolingmode to open the third opening/closing valve, close the fourthopening/closing valve, thereby send the refrigerant discharged from thecompressor from the radiator to the outdoor heat exchanger, let therefrigerant radiate heat in the outdoor heat exchanger, decompress therefrigerant from which the heat has been radiated, through the indoorexpansion valve, and then let the refrigerant absorb heat in the heatabsorber, and a maximum cooling mode to close the third opening/closingvalve and the outdoor expansion valve, open the fourth opening/closingvalve, thereby send the refrigerant discharged from the compressor fromthe bypass pipe to the outdoor heat exchanger, let the refrigerantradiate heat, decompress the refrigerant from which the heat has beenradiated, through the indoor expansion valve, and then let therefrigerant absorb heat in the heat absorber.

The vehicle air conditioner of the invention of claim 4 is characterizedin that in the above invention, the second operation mode is thedehumidifying and heating mode, and the control device executes arefrigerant scavenging operation to open the outdoor expansion valve andenlarge a valve position thereof for a predetermined period of timeafter the mode is shifted to the dehumidifying and heating mode.

The vehicle air conditioner of the invention of claim 5 is characterizedin that in the above invention, the control device maintains a lownumber of revolution of the compressor until the outdoor expansion valveis closed after the refrigerant scavenging operation is started, and thecontrol device raises the number of revolution of the compressor afterthe outdoor expansion valve is closed.

The vehicle air conditioner of the invention of claim 6 is characterizedin that in the invention of claim 4 or claim 5, the control devicecloses the third opening/closing valve and opens the fourthopening/closing valve, after the refrigerant scavenging operation isexecuted.

The vehicle air conditioner of the invention of claim 7 is characterizedin that in the invention of claim 4 to claim 6, the control deviceshifts to the dehumidifying and heating mode, and then opens the thirdopening/closing valve at a timing to stop the compressor.

The vehicle air conditioner of the invention of claim 8 is characterizedin that in the above invention, the number of times the control deviceopens the third opening/closing valve is limited.

Advantageous Effect of the Invention

According to the invention, an vehicle air conditioner includes acompressor to compress a refrigerant, an air flow passage through whichair to be supplied to a vehicle interior flows, a radiator to let therefrigerant radiate heat, thereby heating the air to be supplied fromthe air flow passage to the vehicle interior, a heat absorber to let therefrigerant absorb heat, thereby cooling the air to be supplied from theair flow passage to the vehicle interior, an outdoor heat exchangerdisposed outside the vehicle interior, an outdoor expansion valve todecompress the refrigerant flowing out from the radiator and flowinginto the outdoor heat exchanger, an indoor expansion valve to decompressthe refrigerant flowing into the heat absorber, an accumulator connectedto a refrigerant suction side of the compressor, a first opening/closingvalve to send the refrigerant flowing out from the outdoor heatexchanger, through the indoor expansion valve to the heat absorber, asecond opening/closing valve to send the refrigerant flowing out fromthe outdoor heat exchanger to the accumulator without passing the heatabsorber, and a control device, so that this control device switchesbetween and executes a first operation mode to close the firstopening/closing valve, open the second opening/closing valve, therebylet the refrigerant discharged from the compressor radiate heat in theradiator, decompress the refrigerant from which the heat has beenradiated, through the outdoor expansion valve, let the refrigerantabsorb heat in the outdoor heat exchanger, send, to the accumulator, therefrigerant flowing out from this outdoor heat exchanger, and suck therefrigerant from this accumulator into the compressor, and a secondoperation mode to open the first opening/closing valve, close the secondopening/closing valve, thereby decompress the refrigerant flowing outfrom the outdoor heat exchanger through the indoor expansion valve, letthe refrigerant absorb heat in the heat absorber, send, to theaccumulator, the refrigerant flowing out from this heat absorber, andsuck the refrigerant from this accumulator into the compressor. In thevehicle air conditioner, when the control device shifts from the firstoperation mode to the second operation mode, a valve position of theoutdoor expansion valve is reduced for a predetermined period of timebefore the shifting. Consequently, the flow of the refrigerant is dammedup in the radiator and between the radiator and the outdoor expansionvalve, before shifting from the first operation mode to the secondoperation mode, and it is possible to limit the flow of the refrigerantflowing from the outdoor expansion valve through the outdoor heatexchanger into the accumulator.

In consequence, an amount of a liquid refrigerant to be stored in theaccumulator can be decreased before shifting to the second operationmode. Therefore, it is possible to decrease impact of bumping whichoccurs when the control device shifts to the second operation mode and apressure in the accumulator drops. Furthermore, it is possible toeffectively eliminate or inhibit liquid compression in the compressorand generation of noise in the accumulator, it is possible to enhancereliability of the vehicle air conditioner, and it is also possible toeffectively improve comfort of passengers.

In this case, as in the invention of claim 2, the control devicemaintains a high number of revolution of the compressor for apredetermined period of time before shifting to the second operationmode. Consequently, it is possible to rapidly move the refrigerant inthe accumulator into the radiator and from the radiator to the outdoorexpansion valve, and it is possible to speed up the switching betweenthe operation modes.

Here, as in the invention of claim 3, the vehicle air conditionerincludes a bypass pipe bypassing the radiator and the outdoor expansionvalve, to send, directly into the outdoor heat exchanger, therefrigerant discharged from the compressor, a third opening/closingvalve to send the refrigerant discharged from the compressor to theradiator, a fourth opening/closing valve to send the refrigerantdischarged from the compressor to the bypass pipe, and an auxiliaryheating device to heat the air to be supplied from the air flow passageto the vehicle interior, the first operation mode is a heating mode, andin this heating mode, the control device opens the third opening/closingvalve and closes the fourth opening/closing valve, and the secondoperation mode includes any one, any combination or all of adehumidifying and heating mode to close the third opening/closing valveand the outdoor expansion valve, open the fourth opening/closing valve,thereby send the refrigerant discharged from the compressor from thebypass pipe to the outdoor heat exchanger, let the refrigerant radiateheat, decompress the refrigerant from which the heat has been radiated,through the indoor expansion valve, let the refrigerant absorb heat inthe heat absorber, and generate heat in the auxiliary heating device, adehumidifying and cooling mode to open the third opening/closing valve,close the fourth opening/closing valve, thereby send the refrigerantdischarged from the compressor from the radiator to the outdoor heatexchanger, let the refrigerant radiate heat in the radiator and theoutdoor heat exchanger, decompress the refrigerant from which the heathas been radiated, through the indoor expansion valve, and then let therefrigerant absorb heat in the heat absorber, a cooling mode to open thethird opening/closing valve, close the fourth opening/closing valve,thereby send the refrigerant discharged from the compressor from theradiator to the outdoor heat exchanger, let the refrigerant radiate heatin the outdoor heat exchanger, decompress the refrigerant from which theheat has been radiated, through the indoor expansion valve, and then letthe refrigerant absorb heat in the heat absorber, and a maximum coolingmode to close the third opening/closing valve and the outdoor expansionvalve, open the fourth opening/closing valve, thereby send therefrigerant discharged from the compressor from the bypass pipe to theoutdoor heat exchanger, let the refrigerant radiate heat, decompress therefrigerant from which the heat has been radiated, through the indoorexpansion valve, and then let the refrigerant absorb heat in the heatabsorber. At this time, as in the invention of claim 4, the secondoperation mode is the dehumidifying and heating mode, and the controldevice executes a refrigerant scavenging operation to open the outdoorexpansion valve and enlarge a valve position thereof for a predeterminedperiod of time after the mode is shifted to this dehumidifying andheating mode. Also in this case, the second opening/closing valve is notopened, and hence any noise is not generated in the secondopening/closing valve. Therefore, it is possible to prevent or inhibitthe bumping in the accumulator, while avoiding the generation of thenoise in the second opening/closing valve.

In this case, as in the invention of claim 5, the control devicemaintains a low number of revolution of the compressor until the outdoorexpansion valve is closed after the refrigerant scavenging operation isstarted, and the control device raises the number of revolution of thecompressor after the outdoor expansion valve is closed. As in theinvention of claim 6, the control device closes the thirdopening/closing valve and opens the fourth opening/closing valve, afterthe refrigerant scavenging operation is executed. In this case, whenopening the fourth opening/closing valve, it is possible to decrease adifference between a pressure before the fourth opening/closing valveand a pressure after the valve. Consequently, it is possible to avoidthe generation of the noise in opening the fourth opening/closing valve.

Furthermore, as in the invention of claim 7, the control device shiftsto the dehumidifying and heating mode, and then opens the thirdopening/closing valve at a timing to stop the compressor. Consequently,it is possible to eliminate the disadvantage that reverse pressure isapplied to the third opening/closing valve when the compressor stops inthe dehumidifying and heating mode. Also in this case, as in theinvention of claim 8, the number of times the control device opens thethird opening/closing valve is limited, and hence unnecessary openingand closing of the third opening/closing valve can be avoided inadvance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a constitutional view of a vehicle air conditioner of anembodiment to which the present invention is applied (a heating mode, adehumidifying and heating mode, a dehumidifying and cooling mode, and acooling mode);

FIG. 2 is a block diagram of an electric circuit of a controller of thevehicle air conditioner of FIG. 1;

FIG. 3 is a constitutional view when the vehicle air conditioner of FIG.1 is in a MAX cooling mode (the maximum cooling mode); and

FIG. 4 is a timing chart of each device to explain an example of bumpingpreventing control to be executed by the controller of FIG. 2 whenchanging from the heating mode to the dehumidifying and heating mode.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, description will be made as to embodiments of the presentinvention in detail with reference to the drawings.

FIG. 1 shows a constitutional view of a vehicle air conditioner 1 of oneembodiment of the present invention. A vehicle of the embodiment towhich the present invention is applied is an electric vehicle (EV) inwhich an engine (an internal combustion engine) is not mounted, and runswith an electric motor for running which is driven by power charged in abattery (which is not shown in the drawing), and the vehicle airconditioner 1 of the present invention is also driven by the power ofthe battery. Specifically, in the electric vehicle which is not capableof performing heating by engine waste heat, the vehicle air conditioner1 of the embodiment performs a heating mode by a heat pump operation inwhich a refrigerant circuit is used, and furthermore, the conditionerselectively executes respective operation modes of a dehumidifying andheating mode, a dehumidifying and cooling mode, a cooling mode, and aMAX cooling mode (the maximum cooling mode).

It is to be noted that the vehicle is not limited to the electricvehicle, and the present invention is also effective for a so-calledhybrid car in which the engine is used together with the electric motorfor running. Furthermore, needless to say, the present invention is alsoapplicable to a usual car which runs with the engine. Additionally, theabove heating mode is a first operation mode in the present invention,and the dehumidifying and heating mode, the dehumidifying and coolingmode, the cooling mode and the MAX cooling mode are included in a secondoperation mode of the present invention.

The vehicle air conditioner 1 of the embodiment performs airconditioning (heating, cooling, dehumidifying, and ventilation) of avehicle interior of the electric vehicle, and there are successivelyconnected, by a refrigerant pipe 13, an electric type of compressor 2 tocompress a refrigerant, a radiator 4 disposed in an air flow passage 3of an HVAC unit 10 in which vehicle interior air passes and circulates,to send inside the high-temperature high-pressure refrigerant dischargedfrom the compressor 2 via a refrigerant pipe 13G and let thisrefrigerant radiate heat in the vehicle interior, an outdoor expansionvalve 6 constituted of an electric valve to decompress and expand therefrigerant during the heating, an outdoor heat exchanger 7 which isdisposed outside the vehicle interior and performs heat exchange betweenthe refrigerant and outdoor air to function as the radiator during thecooling and to function as an evaporator during the heating, an indoorexpansion valve 8 constituted of an electric valve to decompress andexpand the refrigerant, a heat absorber 9 disposed in the air flowpassage 3 to let the refrigerant absorb heat from interior and exteriorof the vehicle during the cooling and during the dehumidifying, anaccumulator 12, and others, thereby constituting a refrigerant circuitR.

Furthermore, this refrigerant circuit R is charged with a predeterminedamount of refrigerant and a predetermined amount of lubricating oil. Itis to be noted that an outdoor blower 15 is provided in the outdoor heatexchanger 7. The outdoor blower 15 forcibly sends the outdoor airthrough the outdoor heat exchanger 7 to perform the heat exchangebetween the outdoor air and the refrigerant, whereby the outdoor airpasses through the outdoor heat exchanger 7 also during stopping of thevehicle (i.e., a velocity is 0 km/h).

Additionally, the outdoor heat exchanger 7 has a receiver drier portion14 and a subcooling portion 16 successively on a refrigerant downstreamside, a refrigerant pipe 13A extending out from the outdoor heatexchanger 7 is connected to the receiver drier portion 14 via a solenoidvalve 17 (a first opening/closing valve) to be opened during thecooling, and a refrigerant pipe 13B on an outlet side of the subcoolingportion 16 is connected to an inlet side of the heat absorber 9 via theindoor expansion valve 8. It is to be noted that the receiver drierportion 14 and the subcooling portion 16 structurally constitute a partof the outdoor heat exchanger 7.

In addition, the refrigerant pipe 13B between the subcooling portion 16and the indoor expansion valve 8 is disposed in a heat exchange relationwith a refrigerant pipe 13C on an outlet side of the heat absorber 9,and both the pipes constitute an internal heat exchanger 19. Inconsequence, the refrigerant flowing into the indoor expansion valve 8through the refrigerant pipe 13B is cooled (subcooled) by thelow-temperature refrigerant flowing out from the heat absorber 9.

Furthermore, the refrigerant pipe 13A extending out from the outdoorheat exchanger 7 branches to a refrigerant pipe 13D, and this branchingrefrigerant pipe 13D communicates and connects with the refrigerant pipe13C on a downstream side of the internal heat exchanger 19 via asolenoid valve 21 (a second opening/closing valve) to be opened duringthe heating. The refrigerant pipe 13C is connected to the accumulator12, and the accumulator 12 is connected to a refrigerant suction side ofthe compressor 2. Additionally, a refrigerant pipe 13E on an outlet sideof the radiator 4 is connected to an inlet side of the outdoor heatexchanger 7 via the outdoor expansion valve 6.

In addition, a solenoid valve 30 (a third opening/closing valve) to beclosed during the dehumidifying and heating and MAX cooling describedlater is disposed in the refrigerant pipe 13G between a discharge sideof the compressor 2 and an inlet side of the radiator 4. In this case,the refrigerant pipe 13G branches to a bypass pipe 35 on an upstreamside of the solenoid valve 30, and this bypass pipe 35 communicates andconnects with the refrigerant pipe 13E on a downstream side of theoutdoor expansion valve 6 via a solenoid valve 40 (a fourthopening/closing valve) which is to be opened during the dehumidifyingand heating and MAX cooling. The bypass pipe 35, the solenoid valve 30and the solenoid valve 40 constitute a bypass device 45.

Thus, the bypass pipe 35, the solenoid valve 30 and the solenoid valve40 constitute the bypass device 45, so that it is possible to smoothlychange from the dehumidifying and heating mode or the MAX cooling modeto send, directly into the outdoor heat exchanger 7, the refrigerantdischarged from the compressor 2 as described later, to the heatingmode, the dehumidifying and cooling mode or the cooling mode to send,into the radiator 4, the refrigerant discharged from the compressor 2.

Furthermore, in the air flow passage 3 on an air upstream side of theheat absorber 9, respective suction ports such as an outdoor air suctionport and an indoor air suction port are formed (represented by a suctionport 25 in FIG. 1), and in the suction port 25, a suction changingdamper 26 is disposed to change the air to be introduced into the airflow passage 3 to indoor air which is air of the vehicle interior (anindoor air circulating mode) and outdoor air which is air outside thevehicle interior (an outdoor air introducing mode). Furthermore, on anair downstream side of the suction changing damper 26, an indoor blower(a blower fan) 27 is disposed to supply the introduced indoor or outdoorair to the air flow passage 3.

Additionally, in FIG. 1, reference numeral 23 denotes an auxiliaryheater as an auxiliary heating device disposed in the vehicle airconditioner 1 of the embodiment. The auxiliary heater 23 of theembodiment is constituted of a PTC heater which is an electric heater,and disposed in the air flow passage 3 on an air upstream side of theradiator 4 to the flow of the air in the air flow passage 3. Then, whenthe auxiliary heater 23 is energized to generate heat, the air in theair flow passage 3 which flows into the radiator 4 through the heatabsorber 9 is heated. That is, the auxiliary heater 23 becomes aso-called heater core to perform or complement the heating of thevehicle interior.

Furthermore, in the air flow passage 3 on an air upstream side of theauxiliary heater 23, an air mix damper 28 is disposed to adjust a degreeat which the air (the indoor or outdoor air) in the air flow passage 3,flowing into the air flow passage 3 and passed through the heat absorber9, passes through the auxiliary heater 23 and the radiator 4. Further inthe air flow passage 3 on an air downstream side of the radiator 4,there is formed each outlet (represented by an outlet 29 in FIG. 1) offoot, vent or defroster, and in the outlet 29, an outlet changing damper31 is disposed to execute changing control of blowing of the air fromeach outlet mentioned above.

Next, in FIG. 2, reference numeral 32 denotes a controller (ECU) as acontrol device constituted of a microcomputer which is an example of acomputer including a processor, and an input of the controller 32 isconnected to respective outputs of an outdoor air temperature sensor 33which detects an outdoor air temperature (Tam) of the vehicle, anoutdoor air humidity sensor 34 which detects an outdoor air humidity, anHVAC suction temperature sensor 36 which detects a temperature of theair to be sucked from the suction port 25 to the air flow passage 3, anindoor air temperature sensor 37 which detects a temperature of the airof the vehicle interior (the indoor air), an indoor air humidity sensor38 which detects a humidity of the air of the vehicle interior, anindoor air CO₂ concentration sensor 39 which detects a carbon dioxideconcentration of the vehicle interior, an outlet temperature sensor 41which detects a temperature of the air to be blown out from the outlet29 to the vehicle interior, a discharge pressure sensor 42 which detectsa pressure (a discharge pressure Pd) of the refrigerant discharged fromthe compressor 2, a discharge temperature sensor 43 which detects atemperature of the refrigerant discharged from the compressor 2, asuction pressure sensor 44 which detects a pressure of the refrigerantto be sucked into the compressor 2, a suction temperature sensor 55which detects a temperature of the refrigerant to be sucked into thecompressor 2, a radiator temperature sensor 46 which detects atemperature of the radiator 4 (the temperature of the air passed throughthe radiator 4 or the temperature of the radiator 4 itself: a radiatortemperature TH), a radiator pressure sensor 47 which detects arefrigerant pressure of the radiator 4 (the pressure of the refrigerantin the radiator 4 or immediately after the refrigerant flows out fromthe radiator 4: a radiator pressure PCI), a heat absorber temperaturesensor 48 which detects a temperature of the heat absorber 9 (thetemperature of the air passed through the heat absorber 9 or thetemperature of the heat absorber 9 itself: a heat absorber temperatureTe), a heat absorber pressure sensor 49 which detects a refrigerantpressure of the heat absorber 9 (the pressure of the refrigerant in theheat absorber 9 or immediately after the refrigerant flows out from theheat absorber 9), a solar radiation sensor 51 of, e.g., a photo sensorsystem to detect a solar radiation amount into the vehicle, a velocitysensor 52 to detect a moving speed (a velocity) of the vehicle, an airconditioning operating portion 53 to set the changing of a predeterminedtemperature or the switching between operation modes, an outdoor heatexchanger temperature sensor 54 which detects a temperature of theoutdoor heat exchanger 7 (the temperature immediately after therefrigerant flows out from the outdoor heat exchanger 7, or thetemperature of the outdoor heat exchanger 7 itself: an outdoor heatexchanger temperature TXO), and an outdoor heat exchanger pressuresensor 56 which detects a refrigerant pressure of the outdoor heatexchanger 7 (the pressure of the refrigerant in the outdoor heatexchanger 7 or immediately after the refrigerant flows out from theoutdoor heat exchanger 7: an outdoor heat exchanger pressure PXO).Furthermore, the input of the controller 32 is further connected to anoutput of an auxiliary heater temperature sensor 50 which detects atemperature of the auxiliary heater 23 (the temperature immediatelyafter the air is heated by the auxiliary heater 23 or the temperature ofthe auxiliary heater 23: an auxiliary heater temperature Tptc).

On the other hand, an output of the controller 32 is connected to thecompressor 2, the outdoor blower 15, the indoor blower (the blower fan)27, the suction changing damper 26, the air mix damper 28, the outletchanging damper 31, the outdoor expansion valve 6, the indoor expansionvalve 8, the auxiliary heater 23, and the respective solenoid valves,i.e., the solenoid valve 30 (for reheating), the solenoid valve 17 (forthe cooling), the solenoid valve 21 (for the heating) and the solenoidvalve 40 (for bypass). Then, the controller 32 controls these componentson the basis of the outputs of the respective sensors and the settinginput by the air conditioning operating portion 53.

Next, description will be made as to an operation of the vehicle airconditioner 1 of the embodiment having the above constitution. In theembodiment, the controller 32 switches among and executes the respectiveoperation modes of the heating mode, the dehumidifying and heating mode,the dehumidifying and cooling mode, the cooling mode and the MAX coolingmode (the maximum cooling mode). Description will initially be made asto a flow of the refrigerant and an outline of control in each operationmode.

(1) Heating Mode (First Operation Mode)

When the heating mode is selected by the controller 32 (an automaticmode) or a manual operation to the air conditioning operating portion 53(a manual mode), the controller 32 opens the solenoid valve 21 for theheating (the second opening/closing valve) and closes the solenoid valve17 for the cooling (the first opening/closing valve). Furthermore, thecontroller opens the solenoid valve 30 for the reheating and closes thesolenoid valve 40 for the bypass.

Then, the controller operates the compressor 2 and the respectiveblowers 15 and 27, and the air mix damper 28 has a state of sending, tothe auxiliary heater 23 and the radiator 4, all the air in the air flowpassage 3 that is blown out from the indoor blower 27 and passed throughthe heat absorber 9 as shown by a broken line in FIG. 1. In consequence,a high-temperature high-pressure gas refrigerant discharged from thecompressor 2 flows into the radiator 4 through the solenoid valve 30 andthe refrigerant pipe 13G. The air in the air flow passage 3 passesthrough the radiator 4, and hence the air in the air flow passage 3heats by the high-temperature refrigerant in the radiator 4 (in theauxiliary heater 23 and the radiator 4, when the auxiliary heater 23operates), whereas the refrigerant in the radiator 4 has the heat takenby the air and is cooled to condense and liquefy.

The refrigerant liquefied in the radiator 4 flows out from the radiator4 and then flows through the refrigerant pipe 13E to reach the outdoorexpansion valve 6. The refrigerant flowing into the outdoor expansionvalve 6 is decompressed therethrough, and then flows into the outdoorheat exchanger 7. The refrigerant flowing into the outdoor heatexchanger 7 evaporates, and the heat is pumped up from the outdoor airpassed by running or the outdoor blower 15. In other words, therefrigerant circuit R functions as a heat pump. Then, thelow-temperature refrigerant flowing out from the outdoor heat exchanger7 flows through the refrigerant pipe 13A, the solenoid valve 21 and therefrigerant pipe 13D, and flows from the refrigerant pipe 13C into theaccumulator 12 to perform gas-liquid separation therein, and then thegas refrigerant is sucked into the compressor 2, thereby repeating thiscirculation. That is, the refrigerant flowing out from the outdoor heatexchanger 7 flows through the accumulator 12 without passing the heatabsorber 9. Then, the air heated in the radiator 4 (in the auxiliaryheater 23 and the radiator 4, when the auxiliary heater 23 operates) isblown out from the outlet 29, thereby performing the heating of thevehicle interior.

The controller 32 calculates a target radiator pressure PCO (a targetvalue of the radiator pressure PCI) from a target radiator temperatureTCO (a target value of the radiator temperature TH) calculated from anafter-mentioned target outlet temperature TAO, and controls a number ofrevolution of the compressor 2 on the basis of the target radiatorpressure PCO and the refrigerant pressure of the radiator 4 which isdetected by the radiator pressure sensor 47 (the radiator pressure PCIthat is a high pressure of the refrigerant circuit R). Furthermore, thecontroller 32 controls a valve position of the outdoor expansion valve 6on the basis of the temperature (the radiator temperature TH) of theradiator 4 which is detected by the radiator temperature sensor 46 andthe radiator pressure PCI detected by the radiator pressure sensor 47,and controls a subcool degree SC of the refrigerant in an outlet of theradiator 4. The target radiator temperature TCO is basically TCO=TAO,but a predetermined limit of controlling is provided.

Furthermore, in this heating mode, when a heating capability by theradiator 4 runs short to a heating capability required for vehicleinterior air conditioning, the controller 32 controls the energizationof the auxiliary heater 23 to complement the shortage by the heatgeneration of the auxiliary heater 23. In consequence, comfortablevehicle interior heating is achieved, and frosting of the outdoor heatexchanger 7 is inhibited. At this time, the auxiliary heater 23 isdisposed on the air upstream side of the radiator 4, and hence the airflowing through the air flow passage 3 is passed through the auxiliaryheater 23 before the radiator 4.

Here, if the auxiliary heater 23 is disposed on the air downstream sideof the radiator 4 and when the auxiliary heater 23 is constituted of thePTC heater as in the embodiment, the temperature of the air flowing intothe auxiliary heater 23 rises due to the radiator 4. Therefore, aresistance value of the PTC heater increases, and a current valuedecreases to also decrease an amount of heat to be generated, but theauxiliary heater 23 is disposed on the air upstream side of the radiator4, so that it is possible to sufficiently exert a capability of theauxiliary heater 23 constituted of the PTC heater as in the embodiment.

(2) Dehumidifying and Heating Mode (Second Operation Mode)

Next, in the dehumidifying and heating mode, the controller 32 opens thesolenoid valve 17 and closes the solenoid valve 21. Furthermore, thecontroller closes the solenoid valve 30, opens the solenoid valve 40,and adjusts the valve position of the outdoor expansion valve 6 to ashutoff position. Then, the controller operates the compressor 2 and therespective blowers 15 and 27. As shown by the broken line in FIG. 1, theair mix damper 28 achieves a state of sending, to the auxiliary heater23 and the radiator 4, all the air in the air flow passage 3 that isblown out from the indoor blower 27 and passed through the heat absorber9.

In consequence, the high-temperature high-pressure gas refrigerantdischarged from the compressor 2 to the refrigerant pipe 13G flows intothe bypass pipe 35 without flowing toward the radiator 4, and flowsthrough the solenoid valve 40 to reach the refrigerant pipe 13E on thedownstream side of the outdoor expansion valve 6. At this time, theoutdoor expansion valve 6 is shut off, and hence the refrigerant flowsinto the outdoor heat exchanger 7. The refrigerant flowing into theoutdoor heat exchanger 7 is cooled by running therein or the outdoor airpassed through the outdoor blower 15, to condense. The refrigerantflowing out from the outdoor heat exchanger 7 flows from the refrigerantpipe 13A through the solenoid valve 17 successively into the receiverdrier portion 14 and the subcooling portion 16. Here, the refrigerant issubcooled.

The refrigerant flowing out from the subcooling portion 16 of theoutdoor heat exchanger 7 enters the refrigerant pipe 13B and flowsthrough the internal heat exchanger 19 to reach the indoor expansionvalve 8. The refrigerant is decompressed through the indoor expansionvalve 8, and then flows into the heat absorber 9 to evaporate. By a heatabsorbing operation at this time, the air blown out from the indoorblower 27 is cooled, and water in the air coagulates to adhere to theheat absorber 9. Therefore, the air in the air flow passage 3 is cooledand dehumidified. The refrigerant evaporated in the heat absorber 9flows through the internal heat exchanger 19 and the refrigerant pipe13C to reach the accumulator 12, and flows therethrough to be suckedinto the compressor 2, thereby repeating the circulation.

At this time, the valve position of the outdoor expansion valve 6 isadjusted to the shutoff position, so that it is possible to inhibit orprevent the disadvantage that the refrigerant discharged from thecompressor 2 flows from the outdoor expansion valve 6 back into theradiator 4. Consequently, it is possible to inhibit or eliminatedecrease of an amount of the refrigerant to be circulated, therebyacquiring an air conditioning capability. Furthermore, in thisdehumidifying and heating mode, the controller 32 energizes theauxiliary heater 23 to generate heat. Consequently, the air cooled anddehumidified in the heat absorber 9 is further heated in a process ofpassing the auxiliary heater 23, and hence a temperature rises, therebyperforming the dehumidifying and heating of the vehicle interior.

The controller 32 controls the number of revolution of the compressor 2on the basis of the temperature (the heat absorber temperature Te) ofthe heat absorber 9 which is detected by the heat absorber temperaturesensor 48 and a target heat absorber temperature TEO that is a targetvalue of the heat absorber temperature, and the controller controls theenergization (the heat generation) of the auxiliary heater 23 on thebasis of the auxiliary heater temperature Tptc detected by the auxiliaryheater temperature sensor 50 and the above-mentioned target radiatortemperature TCO. Consequently, the drop of the temperature of the airblown out from the outlet 29 to the vehicle interior is accuratelyprevented by the heating of the auxiliary heater 23, while appropriatelyperforming the cooling and dehumidifying of the air in the heat absorber9.

In consequence, the temperature of the air blown out to the vehicleinterior can be controlled at an appropriate heating temperature whiledehumidifying the air, and it is possible to achieve comfortable andefficient dehumidifying and heating of the vehicle interior.Furthermore, as described above, in the dehumidifying and heating mode,the air mix damper 28 has a state of sending, through the auxiliaryheater 23 and the radiator 4, all the air in the air flow passage 3.Therefore, the air passed through the heat absorber 9 is efficientlyheated by the auxiliary heater 23, thereby improving energy savingproperties, and controllability of the air conditioning for thedehumidifying and heating can improve.

It is to be noted that the auxiliary heater 23 is disposed on the airupstream side of the radiator 4, and hence the air heated by theauxiliary heater 23 passes through the radiator 4. However, in thisdehumidifying and heating mode, the refrigerant does not flow throughthe radiator 4, and hence it is possible to eliminate the disadvantagethat heat is absorbed, by the radiator 4, from the air heated by theauxiliary heater 23. Specifically, it is possible to inhibit thetemperature drop of the air blown out to the vehicle interior by theradiator 4, and a coefficient of performance (COP) improves.

(3) Dehumidifying and Cooling Mode (Second Operation Mode)

Next, in the dehumidifying and cooling mode, the controller 32 opens thesolenoid valve 17 and closes the solenoid valve 21. The controller alsoopens the solenoid valve 30 and closes the solenoid valve 40. Then, thecontroller operates the compressor 2 and the respective blowers 15 and27, and the air mix damper 28 has the state of sending, through theauxiliary heater 23 and the radiator 4, all the air in the air flowpassage 3 that is blown out from the indoor blower 27 and passed throughthe heat absorber 9 as shown by the broken line in FIG. 1. Consequently,the high-temperature high-pressure gas refrigerant discharged from thecompressor 2 flows through the solenoid valve 30 and flows from therefrigerant pipe 13G into the radiator 4. The air in the air flowpassage 3 passes through the radiator 4, and hence the air in the airflow passage 3 is heated by the high-temperature refrigerant in theradiator 4, whereas the refrigerant in the radiator 4 has the heat takenby the air and is cooled to condense and liquefy.

The refrigerant flowing out from the radiator 4 flows through therefrigerant pipe 13E to reach the outdoor expansion valve 6, and flowsthrough the outdoor expansion valve 6 controlled to slightly open, toflow into the outdoor heat exchanger 7. The refrigerant flowing into theoutdoor heat exchanger 7 is cooled by the running therein or the outdoorair passed through the outdoor blower 15, to condense. The refrigerantflowing out from the outdoor heat exchanger 7 flows from the refrigerantpipe 13A through the solenoid valve 17 to successively flow into thereceiver drier portion 14 and the subcooling portion 16. Here, therefrigerant is subcooled.

The refrigerant flowing out from the subcooling portion 16 of theoutdoor heat exchanger 7 enters the refrigerant pipe 13B and flowsthrough the internal heat exchanger 19 to reach the indoor expansionvalve 8. The refrigerant is decompressed through the indoor expansionvalve 8 and then flows into the heat absorber 9 to evaporate. The waterin the air blown out from the indoor blower 27 coagulates to adhere tothe heat absorber 9 by the heat absorbing operation at this time, andhence the air is cooled and dehumidified.

The refrigerant evaporated in the heat absorber 9 flows through theinternal heat exchanger 19 and the refrigerant pipe 13C to reach theaccumulator 12, and flows therethrough to be sucked into the compressor2, thereby repeating this circulation. In this dehumidifying and coolingmode, the controller 32 does not energize the auxiliary heater 23, andhence the air cooled and dehumidified in the heat absorber 9 is reheatedin the process of passing the radiator 4 (a radiation capability islower than that during the heating). Consequently, the dehumidifying andcooling of the vehicle interior is performed.

The controller 32 controls the number of revolution of the compressor 2on the basis of the temperature of the heat absorber 9 (the heatabsorber temperature Te) which is detected by the heat absorbertemperature sensor 48, also controls the valve position of the outdoorexpansion valve 6 on the basis of the above-mentioned high pressure ofthe refrigerant circuit R, and controls the refrigerant pressure of theradiator 4 (the radiator pressure PCI).

(4) Cooling Mode (Second Operation Mode)

Next, in the cooling mode, the controller 32 adjusts the valve positionof the outdoor expansion valve 6 to a fully opened position in the abovestate of the dehumidifying and cooling mode. It is to be noted that thecontroller 32 controls the air mix damper 28 to adjust a ratio at whichthe air in the air flow passage 3, blown out from the indoor blower 27and passed through the heat absorber 9, passes through the auxiliaryheater 23 and the radiator 4 as shown by a solid line in FIG. 1.Furthermore, the controller 32 does not energize the auxiliary heater23.

In consequence, the high-temperature high-pressure gas refrigerantdischarged from the compressor 2 flows through the solenoid valve 30 andflows from the refrigerant pipe 13G into the radiator 4, and therefrigerant flowing out from the radiator 4 flows through therefrigerant pipe 13E to reach the outdoor expansion valve 6. At thistime, the outdoor expansion valve 6 is fully opened, and hence therefrigerant passes the outdoor expansion valve to flow into the outdoorheat exchanger 7 as it is, in which the refrigerant is cooled by therunning therein or the outdoor air passed through the outdoor blower 15,to condense and liquefy. The refrigerant flowing out from the outdoorheat exchanger 7 flows from the refrigerant pipe 13A through thesolenoid valve 17 to successively flow into the receiver drier portion14 and the subcooling portion 16. Here, the refrigerant is subcooled.

The refrigerant flowing out from the subcooling portion 16 of theoutdoor heat exchanger 7 enters the refrigerant pipe 13B and flowsthrough the internal heat exchanger 19 to reach the indoor expansionvalve 8. The refrigerant is decompressed through the indoor expansionvalve 8 and then flows into the heat absorber 9 to evaporate. By theheat absorbing operation at this time, the air blown out from the indoorblower 27 is cooled. Furthermore, the water in the air coagulates toadhere to the heat absorber 9.

The refrigerant evaporated in the heat absorber 9 flows through theinternal heat exchanger 19 and the refrigerant pipe 13C to reach theaccumulator 12, and flows therethrough to be sucked into the compressor2, thereby repeating this circulation. The air cooled and dehumidifiedin the heat absorber 9 is blown out from the outlet 29 to the vehicleinterior (a part of the air passes the radiator 4 to perform heatexchange), thereby performing the cooling of the vehicle interior. Inthis cooling mode, the controller 32 also controls the number ofrevolution of the compressor 2 on the basis of the temperature of theheat absorber 9 (the heat absorber temperature Te) which is detected bythe heat absorber temperature sensor 48 and the target heat absorbertemperature TEO that is the target value of the heat absorbertemperature.

(5) MAX Cooling Mode (Maximum Cooling Mode: Second Operation Mode)

Next, in the MAX cooling mode that is the maximum cooling mode, thecontroller 32 opens the solenoid valve 17 and closes the solenoid valve21. The controller also closes the solenoid valve 30, opens the solenoidvalve 40, and adjusts the valve position of the outdoor expansion valve6 to the shutoff position. Then, the controller operates the compressor2 and the respective blowers 15 and 27, and the air mix damper 28 has astate where the air in the air flow passage 3 does not pass through theauxiliary heater 23 and the radiator 4 as shown in FIG. 3. However, evenwhen the air slightly passes, there are not any problems. Furthermore,the controller 32 does not energize the auxiliary heater 23.

In consequence, the high-temperature high-pressure gas refrigerantdischarged from the compressor 2 to the refrigerant pipe 13G flows intothe bypass pipe 35 without flowing toward the radiator 4, and flowsthrough the solenoid valve 40 to reach the refrigerant pipe 13E on thedownstream side of the outdoor expansion valve 6. At this time, theoutdoor expansion valve 6 is shut off, and hence the refrigerant flowsinto the outdoor heat exchanger 7. The refrigerant flowing into theoutdoor heat exchanger 7 is cooled by running therein or the outdoor airpassed through the outdoor blower 15, to condense. The refrigerantflowing out from the outdoor heat exchanger 7 flows from the refrigerantpipe 13A through the solenoid valve 17 successively into the receiverdrier portion 14 and the subcooling portion 16. Here, the refrigerant issubcooled.

The refrigerant flowing out from the subcooling portion 16 of theoutdoor heat exchanger 7 enters the refrigerant pipe 13B and flowsthrough the internal heat exchanger 19 to reach the indoor expansionvalve 8. The refrigerant is decompressed through the indoor expansionvalve 8 and then flows into the heat absorber 9 to evaporate. By theheat absorbing operation at this time, the air blown out from the indoorblower 27 is cooled. Furthermore, the water in the air coagulates toadhere to the heat absorber 9, and hence the air in the air flow passage3 is dehumidified. The refrigerant evaporated in the heat absorber 9flows through the internal heat exchanger 19 and the refrigerant pipe13C to reach the accumulator 12, and flows therethrough to be suckedinto the compressor 2, thereby repeating the circulation. At this time,the outdoor expansion valve 6 is shut off, so that it is similarlypossible to inhibit or prevent the disadvantage that the refrigerantdischarged from the compressor 2 flows from the outdoor expansion valve6 back into the radiator 4. Consequently, it is possible to inhibit oreliminate the decrease of the amount of the refrigerant to becirculated, and it is possible to acquire the air conditioningcapability.

Here, in the above-mentioned cooling mode, the high-temperaturerefrigerant flows through the radiator 4, and hence direct heatconduction from the radiator 4 to the HVAC unit 10 considerably occurs,but the refrigerant does not flow through the radiator 4 in this MAXcooling mode. Therefore, the air from the heat absorber 9 in the airflow passage 3 is not heated by heat transmitted from the radiator 4 tothe HVAC unit 10. Consequently, powerful cooling of the vehicle interioris performed, and especially under an environment where the outdoor airtemperature Tam is high, the vehicle interior can rapidly be cooled toachieve the comfortable air conditioning of the vehicle interior. Alsoin this MAX cooling mode, the controller 32 controls the number ofrevolution of the compressor 2 on the basis of the temperature of theheat absorber 9 (the heat absorber temperature Te) which is detected bythe heat absorber temperature sensor 48 and the target heat absorbertemperature TEO that is the target value of the heat absorbertemperature.

(6) Switching Between Operation Modes

The air circulated in the air flow passage 3 is subjected to the coolingfrom the heat absorber 9 and a heating operation from the radiator 4(and the auxiliary heater 23) (adjusted by the air mix damper 28) in theabove respective operation modes, and the air is blown out from theoutlet 29 into the vehicle interior. The controller 32 calculates thetarget outlet temperature TAO on the basis of the outdoor airtemperature Tam detected by the outdoor air temperature sensor 33, thetemperature of the vehicle interior which is detected by the indoor airtemperature sensor 37, the blower voltage, the solar radiation amountdetected by the solar radiation sensor 51 and others, and the targetvehicle interior temperature (the predetermined temperature) set in theair conditioning operating portion 53. The controller switches among therespective operation modes, and controls the temperature of the airblown out from the outlet 29 at this target outlet temperature TAO.

In this case, the controller 32 changes from the heating mode to thedehumidifying and heating mode, from the dehumidifying and heating modeto the dehumidifying and cooling mode, from the dehumidifying andcooling mode to the cooling mode, from the cooling mode to the MAXcooling mode, from this MAX cooling mode to the cooling mode, from thecooling mode to the dehumidifying and cooling mode, from thedehumidifying and cooling mode to the dehumidifying and heating mode,and from the dehumidifying and heating mode to the heating mode on thebasis of parameters such as the outdoor air temperature Tam, thehumidity of the vehicle interior, the target outlet temperature TAO, theradiator temperature TH, the target radiator temperature TCO, the heatabsorber temperature Te, the target heat absorber temperature TEO, andpresence/absence of requirement for the dehumidifying of the vehicleinterior. Furthermore, there is also a case where the controller changesfrom the heating mode to the dehumidifying and cooling mode or thecooling mode, and from the dehumidifying and cooling mode or the coolingmode to the heating mode. In the embodiment, the controller changes therespective operation modes as described above, to accurately switchamong the heating mode, the dehumidifying and heating mode, thedehumidifying and cooling mode, the cooling mode and the MAX coolingmode in accordance with environment conditions or necessity for thedehumidifying, thereby achieving comfortable and efficient airconditioning of the vehicle interior.

(7) Bumping Preventing Control at Change from Heating Mode toDehumidifying and Heating Mode and Refrigerant Scavenging Operation

Next, description will be made as to bumping preventing control and arefrigerant scavenging operation which are to be executed by thecontroller 32 at the change from the above heating mode (the firstoperation mode) to the dehumidifying and heating mode (the secondoperation mode), with reference to FIG. 4.

(7-1) Bumping Preventing Control

Here, as described above, the refrigerant and oil flowing out from thecompressor 2 through the refrigerant circuit R flow into the accumulator12 when the compressor 2 is stopped, their liquid part is accumulated inthe accumulator 12, and the oil having a smaller specific weight forms alayer on the liquid refrigerant, thereby bringing about a state like astate of being closed with a lid. Particularly, in the heating mode,there increase amounts of the liquid refrigerant and oil which flow outfrom the outdoor heat exchanger 7 through the solenoid valve 21 into theaccumulator 12 and are accumulated therein.

In this state, when the operation mode changes from the heating mode tothe dehumidifying and heating mode, the refrigerant flowing out from theoutdoor heat exchanger 7 flows from the solenoid valve 17 in a directionof the indoor expansion valve 8. Then, the compressor 2 sucks therefrigerant in the accumulator 12, and hence a pressure in theaccumulator 12 rapidly drops. Then, bumping occurs where the refrigerantbelow the oil boils and vaporizes without stopping, and intensely breaksthrough the upper oil layer, thereby causing excessive liquid return tothe compressor 2 and generating sound (noise).

To eliminate the problems, the controller 32 executes the bumpingpreventing control which will be described below, when changing from theheating mode to the dehumidifying and heating mode. Description will bemade as to an example of the bumping preventing control to be executedby the controller 32 when changing the operation mode of the vehicle airconditioner 1 from the above-mentioned heating mode (the first operationmode) to the dehumidifying and heating mode (the second operation mode).A timing chart of FIG. 4 shows a number of revolution NC of thecompressor 2, the valve position of the outdoor expansion valve 6, andstates of the solenoid valve 40, the solenoid valve 30, the solenoidvalve 17, the solenoid valve 21 and the auxiliary heater 23 duringshifting from the heating mode to the dehumidifying and heating mode.

The valve position of the outdoor expansion valve 6 is reduced (adjustedto a minimum position of controlling in the embodiment) for apredetermined period of time (set to a first predetermined period oftime T1) before the controller 32 shifts from the heating mode to thedehumidifying and heating mode. Furthermore, for this predeterminedperiod of time (T1), the controller raises a lower limit of an operationrange of the number of revolution NC of the compressor 2 (FIG. 4), andmaintains a high number of revolution NC of the compressor 2.

Thus, the valve position of the outdoor expansion valve 6 is reducedbefore shifting from the heating mode to the dehumidifying and heatingmode. Consequently, most of the refrigerant discharged from thecompressor 2 is dammed up in the radiator 4 and the refrigerant pipe 13Ebetween the radiator 4 and the outdoor expansion valve 6 (actuallyincluding the pipe 13G between the solenoid valve 30 and the radiator4), and the subcool degree SC of the refrigerant in the radiator 4increases. Therefore, it is possible to limit the flow of therefrigerant flowing from the outdoor expansion valve 6 through theoutdoor heat exchanger 7 and the solenoid valve 21 into the accumulator12.

In consequence, an amount of a liquid refrigerant to be stored in theaccumulator 12 is decreased before shifting to the dehumidifying andheating mode. Therefore, there decreases impact of bumping which occurswhen the control device shifts to the dehumidifying and heating mode anda pressure in the accumulator 12 drops as described later, therebyeffectively eliminating or inhibiting liquid compression in thecompressor 2 and generation of noise in the accumulator 12.Consequently, reliability of the vehicle air conditioner 1 enhances, andcomfort of passengers effectively improves.

In this case, the controller 32 maintains a high number of revolution NCof the compressor 2 for the predetermined period of time (T1) beforeshifting to the dehumidifying and heating mode. Consequently, it ispossible to rapidly move the refrigerant in the accumulator 12 into theradiator 4 and the refrigerant pipe 13E between the radiator 4 and theoutdoor expansion valve 6, and it is possible to speed up the changingto the dehumidifying and heating mode.

(7-2) Refrigerant Scavenging Operation

Furthermore, as described above, in the dehumidifying and heating mode,the solenoid valve 30 is closed and the outdoor expansion valve 6 isalso shut off, thereby reaching a state where any refrigerant is notsent through the radiator 4. Consequently, when the heating mode ischanged to the dehumidifying and heating mode, the refrigerant remainingin the radiator 4 is laid up therein for a long time, and the amount ofthe refrigerant to be circulated decreases. In particular, when thecontroller executes the bumping preventing control as described above,the amount of the refrigerant remaining in the radiator 4 increases.

To eliminate the problem, the controller 32 executes the refrigerantscavenging operation when changing from the heating mode to thedehumidifying and heating mode in the embodiment. After elapse of thepredetermined period of time (T1) of the above-mentioned bumpingpreventing control, this refrigerant scavenging operation is executed.That is, after the elapse of the predetermined period of time (T1) ofthe above-mentioned bumping preventing control, the controller 32firstly closes the solenoid valve 21, and opens the solenoid valve 17(here the dehumidifying and heating mode starts). It is to be noted thatat this point of time, the solenoid valve 30 and the solenoid valve 40are not changed.

Then, the controller 32 starts the refrigerant scavenging operation. Inthis refrigerant scavenging operation, the controller 32 enlarges (e.g.,fully opens) the valve position of the outdoor expansion valve 6 onlyfor a predetermined period of time (set to a second predetermined periodof time T2). This state is similar to a state of the cooling mode.Furthermore, in the embodiment, the controller maintains a low number ofrevolution NC of the compressor 2 (e.g., the minimum number ofrevolution of controlling) at the start of this refrigerant scavengingoperation.

Consequently, the refrigerant present in a region from the solenoidvalve 30 to the outdoor expansion valve 6 which includes the radiator 4is expelled in a direction of the outdoor heat exchanger 7 (scavenging).Then, after elapse of the predetermined period of time (T2), thecontroller ends the refrigerant scavenging operation, closes thesolenoid valve 30, opens the solenoid valve 40, and closes the outdoorexpansion valve 6 toward the shutoff position. Thus, the outdoorexpansion valve 6 is shut off, and then the controller 32 shifts to astate of controlling the number of revolution of the compressor 2 in anoperation range of the dehumidifying and heating mode. By such arefrigerant scavenging operation, the refrigerant is prevented frombeing laid up for a long time in the radiator 4 or the like, and theamount of the refrigerant to be circulated in the refrigerant circuit Ris acquired to prevent deterioration of an air conditioning performance.

Furthermore, the controller 32 executes the refrigerant scavengingoperation, closes the solenoid valve 30, opens the solenoid valve 40,and maintains a low number of revolution NC of the compressor 2 untilthe outdoor expansion valve 6 is closed after the refrigerant scavengingoperation is started. Then, the controller closes the outdoor expansionvalve 6 and then raises the number of revolution of the compressor 2.Consequently, when opening the solenoid valve 40, it is possible todecrease a difference between a pressure before the solenoid valve 40(on an upstream side) and a pressure after the solenoid valve (on adownstream side). In consequence, the generation of the noise in openingthe solenoid valve 40 is avoided.

Here, according to the embodiment, in the dehumidifying and heatingmode, the controller 32 executes the refrigerant scavenging operation toopen the outdoor expansion valve 6 and enlarge its valve position forthe predetermined period of time (T2) after the mode is shifted to thedehumidifying and heating mode. Therefore, a high pressure is present inthe outdoor heat exchanger 7 and a low pressure is in the accumulator12. However, the solenoid valve 21 is not opened during this refrigerantscavenging operation, and hence any noise is not generated in thesolenoid valve 21. Consequently, according to the embodiment, it ispossible to prevent or inhibit the bumping in the accumulator 12, whileavoiding the generation of the noise in the solenoid valve 21.

(8) Control of Solenoid Valve 30 in Dehumidifying and Heating Mode

Furthermore, in the dehumidifying and heating mode, the auxiliary heater23 generates heat as described above. Then, the refrigerant also remainsin the radiator 4 or the like. Therefore, when the compressor 2 stopsand the pressure on the upstream side of the solenoid valve 30 (on adischarge side of the compressor 2) lowers, the pressure might be higheron the downstream side of the solenoid valve 30 (on a radiator 4 side).In such a reverse pressure state, there is a risk of the generation ofthe noise in the solenoid valve 30. In consequence, the controller 32shifts to the dehumidifying and heating mode and then opens the solenoidvalve 30 at a timing to stop the compressor 2. This eliminates thedisadvantage that reverse pressure is applied to the solenoid valve 30.

However, the controller 32 executes this control to open the solenoidvalve 30, for example, until second timing to stop the compressor 2after the mode is shifted to the dehumidifying and heating mode.Consequently, unnecessary opening and closing of the solenoid valve 30are avoided (however, maybe once or three times or more).

It is to be noted that in the embodiment, the present invention isapplied to the vehicle air conditioner 1 to switch among and execute therespective operation modes of the heating mode, the dehumidifying andheating mode, the dehumidifying and cooling mode, the cooling mode andthe MAX cooling mode, but the present invention is not limited to theembodiment. The present invention is also effective in changing andexecuting the heating mode, one of the other operation modes or anycombination thereof. That is, in the embodiment, also when shifting fromthe heating mode to the dehumidifying and heating mode, the presentinvention is executed, but the present invention may be executed alsoduring shifting to another second operation mode (the dehumidifying andcooling mode, the cooling mode or the MAX cooling mode).

Furthermore, the present invention is not limited to the changingcontrol of the respective operation modes described in the embodiment,and appropriate conditions may be set by employing one, any combinationor all of parameters such as the outdoor air temperature Tam, thehumidity of the vehicle interior, the target outlet temperature TAO, theradiator temperature TH, the target radiator temperature TCO, the heatabsorber temperature Te, the target heat absorber temperature TEO, andthe presence/absence of the requirement for the dehumidifying of thevehicle interior, in accordance with the capability and use environmentof the vehicle air conditioner.

Additionally, the auxiliary heating device is not limited to theauxiliary heater 23 described in the embodiment, and a heating mediumcirculating circuit which circulates a heating medium heated by a heaterto heat air in an air flow passage, a heater core which circulatesradiator water heated by an engine or the like may be utilized.Furthermore, the constitutions of the refrigerant circuit R which aredescribed in the above respective embodiments are not limited thereto,and needless to say, the constitutions are changeable without departingfrom the gist of the present invention.

DESCRIPTION OF REFERENCE NUMERALS

-   -   1 vehicle air conditioner    -   2 compressor    -   3 air flow passage    -   4 radiator    -   6 outdoor expansion valve    -   7 outdoor heat exchanger    -   8 indoor expansion valve    -   9 heat absorber    -   12 accumulator    -   17 solenoid valve (a first opening/closing valve)    -   21 solenoid valve (a second opening/closing valve)    -   23 auxiliary heater (an auxiliary heating device)    -   27 indoor blower (a blower fan)    -   28 air mix damper    -   30 solenoid valve (a third opening/closing valve)    -   40 solenoid valve (a fourth opening/closing valve)    -   32 controller (a control device)    -   35 bypass pipe    -   45 bypass device    -   R refrigerant circuit

The invention claimed is:
 1. A vehicle air conditioner comprising: acompressor to compress a refrigerant, an air flow passage through whichair to be supplied to a vehicle interior flows, a radiator to let therefrigerant radiate heat, thereby heating the air to be supplied fromthe air flow passage to the vehicle interior, a heat absorber to let therefrigerant absorb heat, thereby cooling the air to be supplied from theair flow passage to the vehicle interior, an outdoor heat exchangerdisposed outside the vehicle interior, an outdoor expansion valve todecompress the refrigerant flowing out from the radiator and flowinginto the outdoor heat exchanger, an indoor expansion valve to decompressthe refrigerant flowing into the heat absorber, an accumulator connectedto a refrigerant suction side of the compressor, a first opening/closingvalve to send the refrigerant flowing out from the outdoor heatexchanger, through the indoor expansion valve to the heat absorber, asecond opening/closing valve to send the refrigerant flowing out fromthe outdoor heat exchanger to the accumulator without passing the heatabsorber, and a control device, so that the control device switchesbetween and executes a first operation mode to close the firstopening/closing valve, open the second opening/closing valve, therebylet the refrigerant discharged from the compressor radiate heat in theradiator, decompress the refrigerant from which the heat has beenradiated, through the outdoor expansion valve, let the refrigerantabsorb heat in the outdoor heat exchanger, send, to the accumulator, therefrigerant flowing out from the outdoor heat exchanger, and suck therefrigerant from the accumulator into the compressor, and a secondoperation mode to open the first opening/closing valve, close the secondopening/closing valve, thereby decompress the refrigerant flowing outfrom the outdoor heat exchanger through the indoor expansion valve, letthe refrigerant absorb heat in the heat absorber, send, to theaccumulator, the refrigerant flowing out from the heat absorber, andsuck the refrigerant from the accumulator into the compressor, whereinwhen the control device shifts from the first operation mode to thesecond operation mode, the control device is configured to reduce avalve position of the outdoor expansion valve for a predetermined periodof time before the shifting.
 2. The vehicle air conditioner according toclaim 1, wherein the control device maintains a high number ofrevolutions of the compressor by raising a lower limit of an operationrange of the number of revolutions of the compressor for a predeterminedperiod of time before shifting to the second operation mode.
 3. Thevehicle air conditioner according to claim 1, comprising: a bypass pipebypassing the radiator and the outdoor expansion valve, to send,directly into the outdoor heat exchanger, the refrigerant dischargedfrom the compressor, a third opening/closing valve to send therefrigerant discharged from the compressor to the radiator, a fourthopening/closing valve to send the refrigerant discharged from thecompressor to the bypass pipe, and an auxiliary heating device to heatthe air to be supplied from the air flow passage to the vehicleinterior, wherein the first operation mode is a heating mode, and in theheating mode, the control device opens the third opening/closing valveand closes the fourth opening/closing valve, and the second operationmode includes any one, any combination or all of: a dehumidifying andheating mode to close the third opening/closing valve and the outdoorexpansion valve, open the fourth opening/closing valve, thereby send therefrigerant discharged from the compressor from the bypass pipe to theoutdoor heat exchanger, let the refrigerant radiate heat, decompress therefrigerant from which the heat has been radiated, through the indoorexpansion valve, let the refrigerant absorb heat in the heat absorber,and generate heat in the auxiliary heating device, a dehumidifying andcooling mode to open the third opening/closing valve, close the fourthopening/closing valve, thereby send the refrigerant discharged from thecompressor through the radiator to the outdoor heat exchanger, let therefrigerant radiate heat in the radiator and the outdoor heat exchanger,decompress the refrigerant from which the heat has been radiated,through the indoor expansion valve, and then let the refrigerant absorbheat in the heat absorber, a cooling mode to open the thirdopening/closing valve, close the fourth opening/closing valve, therebysend the refrigerant discharged from the compressor through the radiatorto the outdoor heat exchanger, let the refrigerant radiate heat in theoutdoor heat exchanger, decompress the refrigerant from which the heathas been radiated, through the indoor expansion valve, and then let therefrigerant absorb heat in the heat absorber, and a maximum cooling modeto close the third opening/closing valve and the outdoor expansionvalve, open the fourth opening/closing valve, thereby send therefrigerant discharged from the compressor from the bypass pipe to theoutdoor heat exchanger, let the refrigerant radiate heat, decompress therefrigerant from which the heat has been radiated, through the indoorexpansion valve, and then let the refrigerant absorb heat in the heatabsorber.
 4. The vehicle air conditioner according to claim 3, whereinthe second operation mode is the dehumidifying and heating mode, and thecontrol device executes a refrigerant scavenging operation to open theoutdoor expansion valve and enlarge a valve position thereof for apredetermined period of time after the mode is shifted to thedehumidifying and heating mode.
 5. The vehicle air conditioner accordingto claim 4, wherein the control device maintains a low number ofrevolution of the compressor until the outdoor expansion valve is closedafter the refrigerant scavenging operation is started, and the controldevice raises the number of revolution of the compressor after theoutdoor expansion valve is closed.
 6. The vehicle air conditioneraccording to claim 4, wherein the control device closes the thirdopening/closing valve and opens the fourth opening/closing valve, afterthe refrigerant scavenging operation is executed.
 7. The vehicle airconditioner according to claim 4, wherein the control device shifts tothe dehumidifying and heating mode, and then opens the thirdopening/closing valve at a timing to stop the compressor.
 8. The vehicleair conditioner according to claim 7, wherein the number of times thecontrol device opens the third opening/closing valve is limited to apredetermined number.